Ultrasound is a cyclic sound pressure defined as operating at frequencies above the upper limits of human hearing or above approximately 20 kHz. Ultrasound has been implemented a wide range of applications for imaging, source location determination and range measurements. Many of these applications focus on ultrasound's ability to penetrate a medium and provide structural information of objects within the medium via reflections. Most applications make use of ultrasound by measuring the time delay between when ultrasound is emitted and when echoes are detected. In general terms, the two types of ultrasound systems are pulse echo and continuous wave.